Procedural Potato Chips

[Nerox]

Hi!

Peek into the world of CGI food & learn why proceduralism gets you closer to photo-realistic food.

For non-Houdini minded people (from producers to directors and mom's ;-) I've created a breakdown of how proceduralism works in its simplest form. Obviously Houdini is by leaps and bounds the best solution to put this into practice. Everything is created in Houdini, rendered with Mantra and some minor color correction is applied in Nuke.

So when on your next family gathering your old aunt ask: 'again, tell me what is it that you do?'. You'll just show her this clip and you're done ;-).

[Nerox]

My appologies, it did slip my mind that this is 'geek city' so here we go:

Its rendered with Mantra, I'm using the standard Mantra Surface material as a start but I heavily modified it to create the chips look. Mostly driving spec, displacement, etc with noise patterns.

In terms of rendering settings, it took quite some effort to get that right but the basic settings come down to the default settings with adjustments to:

Engine: PBR

Enabled Depth of Field and Motion Blur

12x12 pixel samples (really couldn't do it with less)

Noise Level 0.001

Reflect limit 2 (the glass objects have overrides on this, mainly increased)

Refract Limit 4 (the glass objects have overrides on this, mainly increased)

Color space: Gamma 2.2

Z-importance: 1 (to get the displacements right, if I remember it correctly)

Yes, the chips take ages to render. Between 30min to 1 hour and 20min per frame on a dual xeon lastest and greatest machine (Ubuntu 12.04, 6-core CPU E5-2667 @ 2.90GHz, 32gb memory). About 2.3x on recent i7 processors.

[Netvudu]

only at this forum you can get your Procedural Potato Chips! Don´t trust other brands!

[WesleyE]

Looks great Nick! Do think the chips could've had a little bit more detail in the transparancy of the material to break it up when they face the light.

[pclaes]

Nice Procedural Potato chips.

Consider adding some burnt edges and color variation over the surface. Also look at the translucency and bounce light coming through in the shadow areas. The shadow areas don't go grey, but still contain color.

edit: Also in regards to the way they are bent. I'm not sure how they become bent like that, but it does not look fully random. The kind of surface shape they form is a 'saddle' surface, which is one of the strongest structural shapes in architecture -- which makes sense from a manufacturers point of view if you want your chips not to break inside of the bag.

Edited June 25, 2013 by pclaes

[Nerox]

Tnx for the great feedback Guy's :-)

The thing is that I tried those things but it became to realistic aka ugly and not tasty. Since I live in a 'tv commercials world' its vital that it looks good. At some point I decided the project was done because I wanted to move on. Nevertheless I do want to touch on it based on the comments that I have received.

On of the things that made it very difficult to work with are the procedurals that I used inside the shader. I layered 2-3 noise patterns on top of each other sometimes driving another one to get the results I wanted. This made it very hard to control.

My opinion is that if you want to successfully use noise patterns you need to layer them up to avoid people seeing the pattern and breaking the illusion.

Based on this experience I want to do a vop HDA that allows one to mix up to 3 layers of noise by using the common math options (mult, div, add, min, etc) within a single node. With an easy visualization option. Hoping this will make it a lot easier to work with.

Regarding the twist, because that is what it is, yes I agree that can have a bit more attention to. Don't know how though, if you have any suggestions I'm happy to hear them :-)

Edited June 26, 2013 by Nerox

[Netvudu]

yup, layering inside shaders is still one of the top b*tches in Houdini. It should definitely be much much easier.

[Nerox]

Especially because with your everyday shading it would make is so easy to breakup specular and reflections without going to an paint app and anyone ever spotting any patterns.

[Nerox]

I've made a second attempt at creating realistic Potato-Chips.

The mayor innovation in this version is my layered noise .otl, that works in the SHOP and SOP context joined by a preview node for easy previewing and isolating individual layers for tweaking. It allows one to layer 3 different layers of noise, have float and vector outputs, apply various operations to combine the layers and offset the noise patterns by an id input.

I've introduced the idea of a float id attribute, where the rounded number and the fraction can be handled differently. For instance, the whole number can be constant per object or piece, where the float value can be different on a per point basis with only minor differences, allowing for a wide range of artistic control.

I'm using different sets of layered noise for channels like diffuse, spec, displacement and refraction. Part of the trick is to have some sets that share similar patterns. For instance the larger displacement pattern (single layer) is also used to drive the base layer of the diffuse. To get the snowy peaks idea, but then topped up with two different layers to make it look more natural.

I never used the exact same patterns to drive different channels of the shader, people are really good at spotting patterns.

Another feature of the potato-chips shader is that it takes a 'edge' attribute, basically an attribute that has a 0-1 value from the center to the edge. This allows to scale down displacements that are closer to the edge, add burned edges and that sort of stuff.

I found that per piece random slight color offsets help to sell the shot as well. It makes it easier to believe they are real.

Apart from that it was a tremendous amount of testing, I found it so difficult to get the right look. In the process I've created a ton of pringles, those are easy ;-).

The pieces don't feature the 'popped bell' things, because

• A I couldn't get it right on a procedural basis (probably need to create hero pieces for that)
  
• B. This is aimed at clients in the television commercial business and I don't think Lays wants any of these things in its commercials.
  

You can find a detailed article (though aimed on potential clients) on my website

Edited October 15, 2013 by Nerox

[freaq]

very nice, often chips have some "bubbles" that are burst when in the bag. or some cracked/broken chips would really add to the realism for me. (then again for a commercial your client would probably never want that ) finally they seem a bit "floaty" to me.

but overall very nice job I'm nitpicking

[Nerox]

Hi Freaq,

Thanks for your reply, what do you mean with 'floaty'? Its plays in slow-motion, this might pull you off. It has been simulated at 'realtime' using all the real forces and then its timewarped afterwards.

[abvfx]

I think its because the camera seems to be moving at a normal pace if not faster. So if the action is at slow motion it would be hard to tell, so it might seem "floaty". If your camera move was extremely slow it would help sell the slo-mo.

See how fast the camera would move in realtime, im sure it would be ridiculously fast.

Will you be working on the edges of the chips to make them appear jagged and/or burnt. Great work.

[dyei nightmare]

great. now i am hungry, i will think about this while i eat some trash food